The general research objective is to define the chemical structure, distribution, and metabolism of the various inositol-containing phospholipids of fungal membranes and to relate this information to the biological significance of these lipids in the maintenance, growth, and development of various fungi. Primary interest will center on the recently discovered sphingolipids of fungi, some of which contain mannose as well as 1 or 2 moles of phosphoinositol. As well as continuing structural characterization of these lipids, an analytical procedure based on high pressure liquid chromatography will be developed which will be used to screen a variety of fungi for the occurrence of these lipids. An attempt will be made to obtain mutants defective in the metabolism of these lipids. Studies will be carried out to establish the biosynthetic pathway for these inositol-containing phosphosphingolipids. The intracellular distribution of these lipids as well as the timing of their synthesis in the cell cycle will be established. Characterization of the conversion of endogenous and exogenous phosphatidylinositol to extracellular glycerophosphorylinositol by yeast cells will be continued. The timing of the reaction with respect to the cell cycle will be established as well as whether other fungal strains exhibit this reaction which accounts for one-half of the net turnover of phosphatidylinositol in yeast. An attempt will be made to study in vitro the enzymes responsible for this deacylation reaction. Diphosphoinositide and triphosphoinositide are two related lipids whose intracellular concentrations change rapidly in concert with changes in the adenylate energy charge of yeast. An attempt will be made to study in vitro the enzymes responsible for the synthesis and degradation of these lipids; special attention will be devoted to defining the factors that account for the in vivo regulation of concentrations of these lipids.